In short, manpower.
A DDG can do what a CVN can insofar as sustained precision attack within certain geographic limits (but it is expanding).
5300 man ship vs. 200 man ship.
A CG magazine with 500 precision rounds translates to over 100 sorties of loaded out Rhinos.
Tanker hits every 7 days vs. independent ops.
VLS Tomahawk still there as more punch.
50+ CG/DDG vs. 4-5 deployed carriers.
It's a manpower beancounter's wet dream.
Mobile nature? look at the CVOA's in the NAG, everybody knows the limitations/parameters of the CVOA. Small boys have much greater geographic flexibility.
You said it, cost.
I'm not saying small-boys will ever supersede CVN's, at least not in the immediate future, but there is a RMA coming for SWO-daddies.
That's the kind of thing I was getting at, what I wanted to see.
Thanks.